Field of the Invention
The present invention relates to vehicle braking force controllers. For example, the present invention relates to a vehicle braking force controller that uses an electric brake not having mechanical connection between a brake member and a brake pedal, and/or regenerative braking not using braking force based on friction.
Description of Related Art
1. In the case of conventional-type hydraulic brake
A master cylinder is pressed in response to the stroke amount of a brake pedal, i.e. the pedal pressing amount, to increase the hydraulic pressure in the piping, whereby a brake member generates pressing force. When the brake pedal is released, hysteresis is generated mainly due to fluid resistance in pipelines and friction force of the master cylinder. Also in the case where the brake pedal is further pressed after a certain stroke amount has been made and then the brake pedal is retuned, unless the brake pedal is returned by a greater amount, the resultant pressing force does not coincide with the pressing force realized before the brake pedal has been further pressed.
In moderate braking operation as performed during speed adjustment and cruising traveling in towns, minute fluctuation in the stroke amount is offset due to the presence of the hysteresis. Accordingly, unnecessary fluctuation in the vehicle behavior is suppressed, and as a result, passengers' riding comfort is realized. When the brake pedal is released, braking force will remain by the amount corresponding to the hysteresis, and thus, return from the nose dive caused by the braking becomes moderate, and thus, fluctuation in the vehicle attitude becomes moderate. This also contributes to passengers' riding comfort.
2. In the case of a brake device not having mechanical connection between the brake member and the brake pedal
2-1. A technology has been proposed in which after an operation amount of the brake pedal is obtained, hysteresis is realized through signal processing that uses a change rate map (Patent Document 1). This technology uses a map in which the change rate is greater on the releasing-side than on the pressing-side.
2-2. A technology has been proposed in which: based on a pressing force applied on the brake pedal, the state of operation, i.e., whether the operation is a pressing operation, a releasing operation, or a retaining operation, is determined; and hysteresis is provided between a command value for the pressing force in the pressing operation and a command value for the pressing force in the releasing operation (Patent Document 2).
2-3. Technologies have been proposed in which, a member or a mechanism that generates hysteresis is interposed in a reaction force generation mechanism for a brake pedal (Patent Documents 3, 4, and 5). These technologies have been proposed in order to make the feeling of pressing the brake pedal close to that realized with a conventional brake that uses hydraulic pressure.